Paper machine head box having improved balance

ABSTRACT

The head box is fitted with a stationary lower lip and a movable hollow body forming an upper lip. The lower end of the body has been attached to a stationary supporting beam of the head box with a flexible gasket so that a cavity is formed between the supporting beam and a front wall of the body. The cavity forms a closed space, which is limited by the side plates of the head box, the supporting beam, and another flexible gasket between the beam and the upper edge of the movable body, and flexible side gaskets between the side plates and the body. The closed space thus formed is communicating with the inside of the head box through channels in the movable body, which has been connected with a stationary front wall of the head box by a flexible gasket.

[451 Feb. 27, 1973 [54] PAPER MACHINE HEAD BOX HAVING IMPROVED BALANCE [75] Inventor: Taisto Ensio Makela, Karhula, Finland [73] Assignee: A. Ahlstrom Osakeyhtio, Noormarkku, Finland [22] Filed: Apri19, 1971 [21] Appl. No.: 132,786

52 U.S.Cl ..l62/340,l62/347 s1 Int.C1. ..D2lfl/02 58 Field otSearch ..l62/336, 340, 342, 347

2,993,538 Mustonen 3,516,905 6/1970 Dennis et a1. "162/342 X 3,528,882 9/1970 Notbohm ..162/347 X 3,562,106 2/1971 Beck et a1 ..162/347 X 3,645,843 2/1972 Schmaeng 162/347 FOREIGN PATENTS OR APPLICATIONS 1965 France 162/336 1970 Germany Primary Examiner-S. Leon Bashore Assistant Examiner-Alfred DAndrea, Jr. Attorney-Jay L. Chaskin [57] ABSTRACT The head box is fitted with a stationary lower lip and a movable hollow body forming an upper lip. The lower end of the body has been attached to a stationary supporting beam of the head box with a flexible gasket so that a cavity is formed between the supporting beam and a front wall of the body. The cavity forms a closed space, which is limited by the side plates of the head box, the supporting beam, and another flexible gasket between the beam and the upper edge of the movable body, and flexible side gaskets between the side plates and the body. The closed space thus formed is communicating with the inside of the head box through channels in the movable body, which has been connected with a stationary front wall of the head box by a flexible gasket.

4 Claims, 3 Drawing Figures PAPER MACHINE HEAD BOX HAVING IMPROVED BALANCE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to the field of head boxes for paper machines and the like.

2. Description of the Prior Art The stiffness of the head box is of very great importance, especially in broad and fast paper machines, in which the pressure inside the box is high. For example, its movable front wall tends to bend under the influence of the pressure, and this makes it difficult to adjust the lip opening so that the discharged stock can be evenly distributed.

The German publication print No. 1,461,176 introduces a closed head box subject to inside pressure; the wall parts supporting its lips have been stiffened with supporting structures and a counterefi'ect to the bending of the walls is brought about with hydraulic and/or pneumatic devices which have been fitted between the wall in question and the respective supporting structure.

The disadvantage of a structure such as this is its large size since all the hydraulic and/or pneumatic devices have been fitted outside the head box. In addition, this structure requires outside sources of pressure and expensive control equipment in order to obtain the goal of the invention.

These disadvantages do not appear in another known structure in which the supporter of the upper lips of the front wall of the head box has been fitted as a separate part inside the front wall so that the lower ends of the supporters of the front wall and the upper lip have been connected in such a way thatthe pressure of the head box prevails on the front and back sides of the supporters of the upper lip. Thus, the horizontal bending of the upper lip is diminished. Such a structure will not, however, cause a completely even distribution of the pressure since the part of the supporter of the upper lip remaining below the juncture bears a load of several tons. The supporter of the upper lip has a wedgeshaped cross section so that the horizontal change of shape of the upper lip can be compensated to only a limited extent by the stiffness of the material, and the upper lip will bulge out. The upper lip also bends in the vertical direction under the influence of the weight of the supporter and the inside pressure having an effect on the supporter. Consequently, the bending forward of the upper lip can be thus partly compensated, but the bending downward will increase.

SUMMARY OF THE INVENTION According to the invention a support beam is attached to the side walls of the head box to form a cavity together with a flexible gasket connecting the upper and lower portions of the body and the beam; the side walls; and the side gaskets and the cavity communicates with the inside of the head box through channel means in the body.

With the structure according to this invention the disadvantages indicated above have been eliminated by fitting the head box with a movable hollow body supporting the upper lip so that the forces and moments having an effect on the movable body are in a state of balance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cross section of one application of the head box according to the invention;

FIG. 2 shows a longitudinal section along line AA in FIG. 1;

FIG. 3 shows a cross section of an alternative application of the movable front wall according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a head box in which the movable hollow body or front wall is indicated by 1. This front wall can be moved in vertical and horizontal directions by mechanisms not shown in detail. The stationary front wall of the head box 2 is indicated by 3. The supporting beam 4 connecting the side plates 5 of the head box forms, together with the movable front wall 1, the front wall 11 and the flexible gaskets 6 and 7, a boxlike space, which is connected with the inside space of the head box by openings 8 through the front wall. Between the movable front wall 1 and the immovable front wall 3 there is a gasket 9 of flexible material.

The gaskets 10 between the movable front wall 1 and the side plates 5 of the head box 2 shown in FIG. 2 glide along the surface of the side plates when the front wall moves.

The stock level It in the head box is kept constant and the space above the stock level is subject to pressure, in which case the pressure in the space formed by supporting beam 4 and wall 11 is the same as the pressure inside the head box. By adjusting the area of the wall 1 1 subject to pressure to a suitable size, a state of balance is obtained, in which case the horizontal component of the force which is directed at the movable front wall 1 and caused by the inside pressure of the head box equals the force in the opposite direction directed at wall 11. Similarly, by adjusting the area 12 of the pressure-subjected upper part of the movable wall 1 inside the head box 2, determined by gasket 9, to a suitable size, a state of balance between the vertical forces directed at the movable front wall 1 can be obtained, in which case both the pressure and the weight of the front wall itself have a downward effect.

According to the invention, the fixing points fitted on the side plates 5 of the horizontal supporting axle of the movable front wall 1 are situated so that the moments are also in a state of balance.

FIG. 3 shows an alternative structure, in which pressure has an effect also on the surface 13 of the movable front wall 1 outside the head box, causing a force with a downward effect.

The movable front wall is in a state of balance when F,,,,=0, F,, ,,=0 and F, X l,,=0, in which the index is l, 2, 3 n and F the force caused by pressure or weight, F, and F being its horizontal and vertical components, and 1,, is the distance of the plane of influence of the force from the center of the supporting axle, which has been indicated by A in FIG. 3.

Since the forces and moments having an effect on the movable front wall are in a state of mutual balance, the front wall can be constructed so that its structure is light and that it requires less space than the previously known structures. Its moving to another position requires less work than those that have been in use to date since the forces directed at the moving organs are small.

The space formed by wall 11 and supporting beam 4 can be one as shown in the figure or it can be formed of several separate spaces connected with each other.

What is claimed is:

1. An improved head box of the type having a closed chamber with an inlet at the rear end thereof; a bottom; a rear wall; two side walls; a top wall; a front wall; a stationary lower lip at the front edge of the bottom; a movable hollow body forming an upper lip, which together with the side walls and the lower lip forms an outlet opening; means attached to the side walls for positioning the body; side gaskets between the body and the side walls; and a first flexible gasket between the front wall and the movable body, the improvement comprising:

a support beam attached to the side walls and extending therebetween in front of the movable body;

second flexible gaskets connecting the upper and lower parts of the support beam and the body and defining together with the side walls and the side gaskets a cavity, the upper second gasket being displaced from the first gasket connected to the top of the movable body; and

channel means in the body connecting the cavity with the inside of the head box.

2. The improved head box of claim 1, wherein the dimensions of a front wall of the movable body are such as to obtain a state of balance, the horizontal component of a force directed at a rear wall of the body and caused by the inside pressure of the head box being equal to a force in the opposite direction directed at the front wall of the body.

3. The improved head box of claim 1, wherein the area of a top wall of the movable body inside the head box, determined by the first flexible gasket, is dimensioned so that a state of balance is obtained between the vertical forces directed at the movable body.

4. The improved head box of claim 1, wherein the means for positioning the body comprises a horizontal support axis for the movable body fitted on the side walls so that the moments having an effect on the movable body are in a state of balance. 

1. An improved head box of the type having a closed chamber with an inlet at the rear end thereof; a bottom; a rear wall; two side walls; a top wall; a front wall; a stationary lower lip at the front edge of the bottom; a movable hollow body forming an upper lip, which together with the side walls and the lower lip forms an outlet opening; means attached to the side walls for positioning the body; side gaskets between the body and the side walls; and a first flexible gasket between the front wall and the movable body, the improvement comprising: a support beam attached to the side walls and extending therebetween in front of the movable body; second flexible gaskets connecting the upper and lower parts of the support beam and the body and defining together with the side walls and the side gaskets a cavity, the upper second gasket being displaced from the first gasket connected to the top of the movable body; and channel means in the body connecting the cavity with the inside of the head box.
 2. The improved head box of claim 1, wherein the dimensions of a front wall of the movable body are such as to obtain a state of balance, the horizontal component of a force directed at a rear wall of the body and caused by the inside pressure of the head box being equal to a force in the opposite direction directed at the front wall of the body.
 3. The improved head box of claim 1, wherein the area of a top wall of the movable body inside the head box, determined by the first flexible gasket, is dimensioned so that a state of balance is obtained between the vertical forces directed at the movable body.
 4. The improved head box of claim 1, wherein the means for positioning the body comprises a horizontal support axis for the movable body fitted on the side walls so that the moments having an effect on the movable body are in a state of balance. 